There is now a task to take into account public holidays and weekends in the application (Russian Federation). The question is, is there any service where you can get them (at the beginning of each year, for example). I do not want to constantly return to the client and enter these dates into the database.
What you need is called the "Production calendar". In its final form, it does not exist in the official version and is compiled on the basis of the calendar of the year and current legislation.
You can get it, for example, from legal sites (Consultant.ru, Garant.ru, etc.), employment portals (HH.RU, SuperJob.RU, etc.) and others.
What is needed is a service from which you can get dates in a specific format (XML, JSON), and which will not fall off in a year.